As I understand it, the original system as proposed and written by Jose Louis Aresti did in fact stipulate roll directions based on the direction of the arrow on a line. However, that convention was dropped by CIVA/FAI sometime in the 60's, and perhaps earlier.

Since that time the convention has been that the direction of the arrow does not indicate directionality with respect to a left or right roll.

Many people refer to the original Aresti system as written by the good Colonel as "pure" Aresti.